Clinical relevance of different IgG and IgM serum antibody responses to Borrelia burgdorferi after antibiotic therapy for erythema migrans: long-term follow-up study of 113 patients.

OBJECTIVES To investigate the kinetics of anti-Borrelia burgdorferi antibodies for a minimum of 1 year after antibiotic therapy in patients with erythema migrans (EM) and to correlate antibody titer kinetics with clinical variables. DESIGN Retrospective study of serial anti-B burgdorferi antibodies in correlation to clinical variables. SETTING University-based hospital. PATIENTS One hundred thirteen patients with EM. INTERVENTIONS Pretreatment and a median of 4 consecutive posttreatment serum samples from median follow-up of more than 400 days were simultaneously investigated for anti-B burgdorferi IgG and IgM antibodies. Semiquantitative titers were plotted to identify different groups of antibody kinetics. Individual patients were then stratified to those groups according to their antibody development. A statistical comparison of clinical and therapy-related characteristics among the serologic groups was performed. RESULTS Anti-B burgdorferi IgG and IgM antibody titers developed in 3 distinct courses: persistent positivity across follow-up (IgG: 12 patients, 11%; IgM: 14, 12%), persistent negativity (IgG: 63, 56%; IgM: 47, 42%), and decrease of a positive pretreatment titer to a negative titer approximately 5 months after therapy (IgG: 34, 30%; IgM: 49, 43%). Statistics revealed significant correlations only between persistent positive IgG titers and long disease duration or large EM lesions before therapy. CONCLUSIONS Long duration or large size of EM before therapy correlates with persistence of a positive anti- B burgdorferi IgG antibody titer after therapy. Serologic profiles do not depend on the type or duration of therapy or the clinical course thereafter. Thus, antibody testing in the follow-up of patients with EM is inappropriate for the assessment of therapeutic response.